Method of making seamless tubes from columbium containing austenitic chromium nickel alloy steel and product thereof



Patented Nov, 7,1939;

PATENT OFFICE METHOD OF MAKING SEAMILESS TUBES FROM COLUMBIUM CONTAININGAUSTEN- ITIC CHROIVIIUIW NICKEL ALLOY STEEL. AND PRODUCT THEREOF Vere B.Browne, Brackenridge, Pa., assignor to Allegheny Steel Company, acorporation 0 Pennsylvania No Drawing. Application September 12, 1935,Serial No. 40,346

'1 Claims.

This invention relates to a method of makin seamless tubes fromcolumbium-containing austenitic chromium nickel alloy steel and toseamless tubes therebyproduced, the present application being a divisionof my co-pending application Serial No. 17,154, filed April 18, 1935.

- In making seamless tubes from austenitic chromium nickel steels, suchsteels are heated and pierced, in the form of billets, in thetemperature range of 2100-2300 Fahrenheit. Even when their carboncontent is below 0.07%, the

- austenitic chromium nickel steels of the 18-8 type present no especialdifflculty in the production of seamless tubes.

When, however, there is an increase of the position.

As the nickel and chromium are increased the delta ferrite constituentiscorrespondinglyformed at progressively lower temperature. It is,however, impractical and well-nigh impossible to pierce the startingmaterial at a temperature of 2000 F. or lower because the usual piercingmills do not have sufiicient power to force a hole through the billet orstarting material at these low temperatures and even if they had, thereis no known piercing point of sufiicient strength at these temperaturesto effect the piercing operations.

Columbium, as well as various rare elements,-

have been added for stability, but these, including columbium, cause theformation of delta ferrite at temperatures considerably below thosetemperatures at which delta ferrite is formed in steels of the samecomposition whichcontain no columbium or other of the rarer elementswhich have been used. For this reason, commercial and satisfactoryseamless tubes cannot be made even.

when the alloy contains columbium, except in accordance with my presentinvention.

I have discovered that I can successfully hot work columbium-bearing18-8 and also successfully produce seamless tubes therefrom provided thecomposition, excluding the columbium, is

rationally proportioned in a certain manner to be hereinafter set forthand under which circumstances delta ferrite is not formed. attemperatures up to 2300 F. so that seamless tubes can be readilyproduced by conventional methods in the same manner and at the sametemperatures as from alloys or steels containing no columbium. I

It is accordingly an object of the present invention to provide anaustenitic chromium nickel iron alloy or steel containing columbiumwhich can be readily hot worked as, for example, by rolling, forging orpiercing.

Another object of my invention is the production of seamless tubes fromcolumbium-containing austenitic chromium nickel ironalloys without theformation of delta ferrite within the ordinary piercing temperatureranges.

A further object of my invention is, in an austenitic chromium nickeliron alloy or steel containing columbium, to so proportion certain ofthe elements thereof, particularly the chromium and nickel contents, asto avoid the difficulties and problems, which hitherto confronted theart.

make possible the production of physically perfect seamless tubes from acolumbium-containing austenitic chromium nickel iron alloy or steel inthe same manner in which these tubes are produced' from alloys or steelswhich do not con;- tain columbium, i. e., by standard commercialmethods.

Other and further objects and advantages reside in the various detailsto be'hereinafter set forth and such will be understood by those skilledin this art or will be apparent or pointed out hereinafter.

I have discovered that if I add approximately .3-1% of columbium to theaustenitic chromium nickel iron alloys or steels containing about 16-18%of chromium, about -11% of nickel 'and not over about .12% of carbon,with the balance substantially all iron. except for the usualcontaminants in common amounts, and maintain such a relationship betweenchromium and nickel that the ratio is not over 2:1 while maintainingcarbon about to the amount of columbium, I produce material which can bereadily forged, rolled and worked without tearing, breaking, etc. Thematerial can therefore be worked or treated according to standardcommercial practice, a thing which has hitherto been practically impos-A still further object of my' invention is to ,sible or exceedinglydifficult in connection with 1 Chromium Total cliro Chro- Colum- CarbonNickel nlckel mium-l- [mum bium ratio nickel 15 1 090 17. 76 8. 88 1.055 2. O 26. 64 2 08 19. 93 8. 97 l. 82 2. 22 28. 9 3 076 17. 3 7. 67 942. 26 24. 87 4 084 17. 09 9. 96 63 l. 71 27. O

I, therefore, may state as a general proposition that my inventioncomprises a seamless tube composed of an austenitic chromium nickel ironalloy or steel containing about .3-1% of columbium in which the ratio ofchromium to nickel is not more than 2 to 1 and in which the carbon ispreferably less than .12%. Compositions within this definition can besuccessfully hot worked and seamless tubes can be commercially producedby the conventional piercing operations and within the conventionaltemperature range of 2100 to 2300 F. The advantage of the capacity of myalloy to produce satisfactory commercial forms by hot working such asrolling or forging operations or by hot piercing are eviden to thoseversed in this art.

I have discovered that if in an austenitic chromium nickel iron or steelalloy columbium is incorporated within the limits of about .3 to 1% withcarbon preferably under approximately when the ratio of the amount ofchromium to the amount of nickel is not over 2 to 1 there is practicallyno delta ferrite produced when billets of this material are formed byrolling or working and pierced up to 2300 F., so that satisfactoryseamless tubes can be produced from such material by standard commercialpractice. This principle is illustrated by compositions Nos. 1 and 4supra in which it is apparent that the ratio of chromium to nickel isnot over 2 to 1. On the contrary, in compositions Nos. 2 and 3 the ratioof chromium to nickel is respectively 222 to 1 and 2.26 to l, in bothcases the ratio, therefore, being more than 2 to 1. Compositions 2 and 3show delta ferrite at temperatures as low as 2100 F. and even lower andhence will not produce commercial seamless tubes by conventionalcommercial practice.

I am aware that the use of columbium in an austenitic chromium nickeliron alloy or steel is not broadly new with me but, remembering thedefects and difficulties above set forth, it is apparent that I havemade it possible for the art to reduce, by hot rolling and forgingoperations, ingots without excessive breakage and to prepare seamlesstubes commercially by standard methods and from an austenitic alloycontaining columbium by limiting the ratio of chromium to nickel suchthat it is not more than An alloy as described containing .3-1%columbium shows upon microscopical examination that, although columbiumand carbon apparently combine to form columbium carbides, the 5 carbidesare not rejected to the grain boundaries but on the contrary areuniformly distributed through the grains themselves. Because of thisdispersion the new properties and charactertistics are obtained.

In making seamless tubes from the columbiumcontaining alloy or steelabove described, I form billets or other suitable starting pieces in anyknown or desired manner and then pierce the billets or other startingpieces according to standard commercial practice, that is, at 2100-2300F., with the usual piercing points. No breaking or tearing of the tubesoccurs because there is no substantial formation of delta ferrite underthe conditions noted. I have thus for the first time made it possible toproduce, by standard commercial practice, columbium-containingaustenitic alloy seamless tubes and to produce them without any materialpercentage of seconds or defective tubes.

The foregoing is presented as exemplary and not as limitative, the scopeof the invention being rather that set forth by the subjoined claims. Itis clear that I may make certain modifications, variations, omissionsand/or substitutions so long as I remain within the principleshereinabove set forth and my invention not only applies to seamlesstubes but to other articles of manufacture wherein the principlesof thepresent invention find application. By the same token, my inventionincludes a method for producing such seamless tubes wherein, however,the composition used falls within the-principles and scope of thepresent invention. I am, moreover, not restricted to columbium only as Imay utilize equivalents thereof or any other suitable element in thesame group of Mendelejeffs periodic arrangement of the elements.

I do not claim in this application the columbium containing austeniticchromium nickel steel alloy per so since such forms the subject matterof my companion application Ser. No. 17,154, filed April 18, 1935. Nordo I claim in this application the method of making welded products andthe products thereby produced since such forms the basis of my companionapplication Ser. No. 40,276, filed September 12, 1935.

What I claim as new and desire to secure by Letters Patent is:

1. The method of making seamless tubes comprising rolling or workingingots to form billets from an austenitic chromium nickeliron columbiumsteel or alloy containing about 16-18% chromium, about 85-11% nickel butwhere the ratio of chromium to nickel is not over 2:1, and about .3-1%columbium, the balance being substantially all iron except for the usualcontaminants in common amounts, piercing the billets at 2100-2300 F. toform the tubes and thereafter finishing the tubes in required manner.

2. The method of making seamless tubes comprising rolling or workingingots to form billets from an austenitic chromium nickel iron columbiumsteel or alloy containing about 17.76% chromium, about 8.88% nickel,about .09% carbon and about 1.05% columbium, the balance of the steel oralloy being substantially all iron except for the usual contaminants incommon amounts, the ratio between the chromium and nickel being not over2:1, piercing the billets-at 2100 to 2300 F. to form the seamless tubesand thereafter finishing the tubes as required.

3. The method of making seamless tubes comprising rolling orworking-ingots to form billets from an austenitic chromium nickel ironcolumbium steel or alloy containing about 17.09%

chromium, about 9.96% nickel, about .08% carbon and about .63%columbium, the balance of the steel or alloy being substantially alliron except for the usual contaminants in common amounts, the ratiobetween the chromium and nickel being not over 2:1, piercing the billetsat 2100 to 2300 F. to form the seamless tubes and thereafter finishingthe tubes as required.

4. The method of making seamless tubes free from delta ferrite formationwhich comprises making a heat of austenitic chromium nickel columbiumsteel, adjusting the composition of the heat so that the chromiumcontent thereof falls between about 16% and 18%, the nickel contentthereof falls between about 8.5% and 11%, the columbium content thereoffalls between about 0.3% and 1% and the carbon content thereof is notover about .12%, adjusting the relative chromium and nickel contentswithin the above limits so that Cr/Ni is not over 2:1, casting an ingot.having an analysis responding to said heat, forming billets from suchingot, piercing the billets at 2100-2300 F. to form tubes and finishingthe tubes as required.

5. A seamless tube composed of an austenitic steel or alloy containingabout 16-18% chromium,

about -11% nickel, the ratio of chromium to nickel being not more than2: 1, and about 0.3-1% columbium, carbon being not over about 0.12%

about 8.88% nickel, about 0.09% carbon and about 1.05% columbium, thebalance being substantially all iron except for the usual contaminantsin common amounts, the alloy steel being characterized by the fact thatthe ratio of chromium to nickel is not over 2:1, the tube beingcharacterized by freedom from delta ferrite despite its formation bypiercing at temperatures which normally produce delta ferrite.

7. A seamless tube'composed of an austenitic steel or alloy containingabout 17.09% chromium, about 9.96% nickel. about 0.08% carbon and about0.63% columbium, the balance being sub-' despite its formation bypiercing at temperature which normally produce delta ferrite.

, VERE B. BROWNE.

